Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

Damen, M. C. J.

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Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856343064

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: XV, 547 Seiten

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856343064

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 3 Spectral signatures of objects. Chairman: G. Guyot, Liaison: N. J. J. Bunnik

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: A preliminary assessment of an airborne thermal video frame scanning system for environmental engineering surveys. T. J. M. Kennie & C. D. Dale, G. C. Stove

Document type:: Multivolume work

Structure type:: Chapter

more e. be ght a more emera in lore recent ! and involved mount in a iximum i with a • plate was and Stroud •ated through This , The most ;he ibles higher jl lei *y over large pted Wild RC8 craft ita consists ecording to a i to remove i and ;a using ¡rsion of il frame store ;nts are now , The Rations was )P 3000 image sges, were system. One n'que is that of de-striping. This was performed by running a rectangular box filter across the image. The advantage of such a process is to produce a more consistent image. However, since the filter cannot discriminate between small scene variations and systematic and random noise, both tend to be removed or reduced in amplitude. For applications where there is an interest in the detection of subtle linear features, (for example the identification of subterranean field drains), it has been found useful to perform a variable filter edge enhancement, the filter size being dependant on the particular feature of interest. The most commonly used filters range from 3 X 3 to 15 X 15 pixels in dimension. Once the feature of interest has been enhanced by this process it has also been found useful to apply a median filter; this resamples the data in a 3 X 3 box. By using this process isolated pixels caused by the edge enhancement procedure tend to be removed. A further processing operation is required if the project requires quantitative absolute temperature values. In order to obtain such information calibration of the imagery needs to be carried out using ground temperature measurements obtained at the time of the aircraft overpass. Correlation of these ground measurements with the unstretched digital numbers can be used to establish the limits for a quantitative density slice representing discrete temperature levels. The application of this technique to heat loss monitoring is presented in section 6. 6 APPLICATIONS As mentioned previously several flights of the Barr and Stroud IR18 TVFS were performed during August 1984 as part of a preliminary research assessment of the instrument. As a consequence of early morning mist these flights took place from late morning until late afternoon rather than, as planned, during the post-sunset/ pre-dawn period. The imagery obtained was, nevertheless, useful since it enabled the potential of the imagery to be assessed together with methods of processing the imagery (Dele, 1985) More recently both the Barr end Stroud and RPC TVFS systems have been flown, for a variety of projects by ERSAC Ltd. The following material reports some of the most significant applications to date. 6.1 Heat Loss Monitoring. Several projects have been carried out using the Barr and Stroud IR18 to assess heat loss from industrial and residential buildings. As mentioned above, in order to provide quantitative estimates of localised heat loss from TVFS imagery it is necessary to establish calibration data to relate the grey scale variations on the image to emitted radiance and eventually to estimates of heat emission. In addition to deriving emitted temperature it is also necessary to evaluate the variations in emissivity over the scene. Ground temperature measurements can be obtained using either conventional in-situ temperature probes (e.g. thermistors or thermometers) or alternatively by using ground based radiometric measurements from instruments such as the AGA Thermovision. As mentioned earlier the AGA Thermovision is a low spatial resolution system; however, it is possible, by using a blackbody reference, to obtain ground temperature measurements. By using the Stefan- Boltzmann law the heat loss for a particular temperature value can be derived and a suitable density slice for the IR18 imagery obtained. The results of one particular set of date are shown in Table 4. If the computed heat losses (Q) from Table 4 are regressed on the mean digital number indicating emitted radiance (R) from the IR18, then a regression coeffiecient (r) of 0.924 is obtained. The Table 4. Calibration of Heat Loss from Barr and Stroud IR18 using data from the AGA Thermovision Colour Coding Mean Radiance(R) AGA Temperature (*c) Mean Computed Heat Loss (Q) (Watts) Blue 44 2.5 11 Cyan 74 4.0 17 Magenta 80 4.7 21 Grey 95 6.3 28 Black 110 6.5 29 Red 131 7.6 33 White 155 13.8 63 coefficient of determination (r 2 ) is 0.854, indicating that 85% of the computed heat losses from the calibration results above can be explained by the corresponding radiance values (R) as recorded and digitised from the IR18 sensor data. The resulting heat loss regression equation for the IR18, for the 8°c gain setting was of the form; Q = 0.4185R - 12.537 ....(1) with a standard error of ±6 watts. 6.2 Thermal Mapping of Roads A novel environmental engineering application of the IR18 TVFS system has involved thermal mapping of road surfaces in winter to identify accident black spots. The primary objective of this night-time aerial survey work was to assist road engineers in the siting of ground sensors to monitor ice conditions around high accident risk sections of road. It is also hoped that the data will enable improvements and ecomomies in road gritting operations to be achieved. The survey was carried out in Scotland in February 1986. Ground temperature measurements were obtained and used to determine calibration data for the IR18. By using this data in conjunction with the GEMS image processing system it was possible to digitise and calibrate a selected number of frames of data. Using a digital to analogue converter it was then possible to create from these selected scenes, a density sliced video image of the original analogue tape. This feature has been shown to be of considerable benefit to non specialists viewing the imagery. 6.3 Geotechnical Site Investigations An assessment of the potential of the IR18 to detect solution features in chalk will be carried out during the summer of 1986. Solution features are a serious geotechnical hazard and generally provide unreliable bearing capacity for foundations. A review of the significance of solution features end the use of remote sensing techniques for their detection is provided in Kennie and Edmonds (1986). The relative performance of TVFS and thermal infrared linescanning techniques will also be investigated during this exercise. 6.4 Drainage, Sewer Collapse and Utilities Surveys A recent application of the IR18 has involved the detection of subsurface utilities and problems associated with such features. In this case the TVFS was mounted on a boom attached to a car and was used in conjunction with a ground impulse radar system (x = 6 to 330 centimetres).

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